Teardown Tuesday: Motion-Activated Trail Camera

In this Teardown Tuesday, we are going to take a look at the inner workings of a trail camera!

Trail cameras, often referred to as Trail Cams, are popular with hunters and outdoor enthusiasts. They allow people to keep a record of animals, such as dear, nearby. In this teardown Tuesday we are going to take a look at the insides of one of these trail cams!

Opening it Up!

The sealing gasket

This trail cam was easy to open. The removal of Phillips-head screws allowed the two-piece plastic shell to simply pulled apart. The circuit boards are held in place with a few more Phillips-head screws. To make the camera a little more weather-resistant there is a gasket between both halves.

Circuit Boards

The top of the main PCB

There are three circuit boards inside the trail cam. There is a main board that contains most of the electronics and two daughter boards. The circuit board for the display is connected through a 24??? Position ribbon cable. The IR light board is connected through a 6-position wire to board connector.

The bottom of the main PCB

The main board has a black soldermask and a white silkscreen. There are a handful of unpopulated components and jumper wires indicating that this board is most likely used in other similar products with different features.

The top of the board is populated with both surface-mount and through-hole components. The rear of the circuit board has only surface-mount components.

The LCD PCB

The LCD board contains the LCD display and a connector. A square of adhesive foam is used to provide stress relief and padding for the LCD and its associated ribbon cable. The IR light board contains 28 5mm IR LEDs, a 5mm red LED, a photodiode and a handful of surface-mount passives on the solder side of the PCB.

The LED light board

Power Supply

The battery tray

This trail cam relies on eight AA batteries to power it. They are configured in a with four cells in series and two cells in parallel (4S2P). This configuration has a voltage of about 6 volts at 5700mAh for a total energy of 34 wHr, assuming 2850mAh AA cells.

The batteries are inserted into a removable battery tray. The tray connects to the electronics via four spring contacts. The voltage from the batteries is then regulated using a pair of switching power supplies.

The switching power supplies

Motion Sensor and Camera Assembly

The PIR sensor

In order to conserve battery, this trail cam only powers on the camera when motion is detected. To detect motion, it relies on a PIR (passive infrared sensor). These sensors use very little power, in some cases <10uA at 3.3v.

A Fresnel lens is placed in front of the sensor to give it a wider viewing angle. This PIR sensor has a 45-degree viewing angle.

The Fresnel lens for the PIR sensor

If motion is detected, the camera will turn on. The camera module and lens assembly are mounted directly to the PCB, held in place with two screws. This camera module is an advertised as a 5 megapixel CMOS sensor.

The camera module

There is a light filter that is a mounted with adhesive to the front of the camera module and hard soldered to the circuit board. This assembly uses a solenoid to switch between an IR light blocking filter for use during the day and an IR pass filter for use during the night.

The IR filter

On the IR light PCB, there is a photodiode to detect the level of light. If it is dark out, the camera turns on the array of IR lights and moves the IR block filter from in front of the camera. This allows for the camera to see nearby objects in the dark without shining a bright visible light.

The photodiode on the IR LED board

There are 28 5mm IR LEDs on the camera. These LEDs are powered directly from the batteries. There are 14 pairs of series LEDs that are current-limited with a 100-ohm resistor. This would provide around 14mA to each LED for a total current draw of around 400mA. According to the included manual, the IR LEDs have a range of “about 15 m”.

The 5mm IR LEDs

User Interface

The right angle push buttons

To let the user control the trail camera, there are three through-hole right angle tactile switches. These buttons control “Up”, “Down”, and “OK”. There is a three-position side switch that changes the mode between off, photo, and video.

The LCD screen

There is an onboard LCD display that shows the settings menu and lets the user preview the image. This LCD is 1.44” diagonal and is 128 x 128 pixels, giving it a pixel density of about 107ppi (about ⅕ the pixel density of a Samsung Note 8). This display has a date code indicating it was manufactured 8/22/2016.

System-on-a-Chip

The Sunplus SoC

Controlling all of the functions of this trail cam is a Sunplus system-on-a-chip, or SoC. Not a lot can be found about this particular SoC. It is made by Sunplus and carries the part number SPCA1628. Searching reveals that this IC is commonly used in dash cameras. (Check out our dash cam teardown!). There is an external RAM, ESMT M12L128168A, paired to the SoC.

The ESMT RAM

Conclusion

Thanks for taking a look at this trail cam teardown! For $50USD, it is an interesting product. Name-brand trail cameras often cost far more, but have many of the same features. Stop by next Tuesday for another teardown!